1. Field of the Invention
The present invention is related to a laser module having a light source adjustment mechanism used for recording and reproducing conducted on an optical disk, an optical pickup device in which this laser module is used, an optical disk device in which this optical pickup device is used, a focus error detection method of the optical pickup device, and a tracking error detection method of the optical pickup device.
2. Description of the Related Art
In the conventional optical pickup, several types of beam splitters are used so as to separate the light source for emitting light and the optical system for detection from each other. However, there is a strong demand for downsizing the optical pickup in the market. In order meet the demand, a new attempt has been made for providing an optical unit in which the light source and the detection optical system are accommodated in the same package.
In order to realize this optical unit, an optical member, in which the diffraction grating is formed, is used. A specific embodiment of this optical member is disclosed in detail in Patent Document 1 (JP-A-10-154344). Since this optical member has been realized, the optical pickup can be greatly downsized, and a small optical disk device on which the small optical pickup is mounted has been widely spread in the market.
Recently, the optical disk device has been greatly diversified. Therefore, it has become possible to conduct recording and reproducing on both CD (Compact Disk) and DVD (Digital Versatile Disk) with one set of recording and reproducing device. The wave-length of a laser beam used for recording and reproducing CD is different from the wave-length of a laser beam used for recording and reproducing DVD. In order to conduct recording and reproducing on both CD and DVD, it is necessary to use two types of laser beams, the wave-lengths of which are different from each other.
When the downsized optical disk device has been widely spread, the following new problems are caused. For example, since the optical disk device has been downsized, the detection element and the optical member are naturally arranged close to the light source of emitting light. When the optical disk device is used over a long period of time and the use for recording is expanded, an optical output of the light source of emitting light is increased, and the temperature is raised at the same time. Further, as can be seen in the diffusion of the notebook type PC, the optical disk device is accommodated in a small housing, and the ambient temperature of the optical disk device is further raised.
When the ambient temperature range is expanded as described above, an influence is given by the coefficient of thermal expansion to the components composing the optical unit. For example, when the size and position of the optical member composing the diffraction grating are affected by heat, an error or offset is caused in the servo control.
Patent Document 2 (JP-A-2002-175634) discloses an integrated optical member capable of realizing a detecting motion of detecting a signal without affecting the detection optical system by a change in the ambient temperature. Further, Patent Document 2 discloses an optical pickup device in which this integrated optical member is used. Furthermore, Patent Document 2 discloses an optical disk device in which this optical pickup device is used.
In this device, the following problems may be encountered. Unless a laser beam emergent from the laser beam source is emitted in an appropriate direction, an intensity of the laser beam irradiated on to the optical disk is reduced. Therefore, information can not be accurately recorded and reproduced. In order to solve the above problems, it is necessary to adjust a position of the laser beam source. Further, it is also necessary to adjust a posture of laser beam source. However, when the size of the device is reduced, mechanisms to adjust the position and the posture of the laser beam source are restricted. Therefore, it is required that the position and the posture of the laser beam source can be sufficiently adjusted in a small space.
In this device, it is necessary to accurately conduct a signal detecting action to conduct recording and reproducing on CD, and it is also necessary to accurately conduct a signal detecting action to conduct recording and reproducing on DVD. It is necessary that these signal detecting actions are conducted without being affected by a change in the ambient temperature.